If you don't know, interstitial ads are full screen ads used on mobile apps to monetize your app.
Want to know how to use interstitial ads without upsetting Google and your customers ? This video talks a lot about it
Make sure that you do not interrupt the user with an interstitial ads. Also do not place where accidental clicking can happen.
Be careful how you place interstitial ads. If you use click-bait, Google won't take it lightly.